This invention relates to an intake system of a V-type combustion engine, and more particularly to an intake system of a V-type engine which can reduce the height dimension thereof and which is advantageous in mounting on the vehicle.
This invention also relates to an intake system of a V-type engine in which intake passages for low speed and high speed operations are switched according to a driving state of a vehicle, and the intake passage for high speed is inclined toward a center of the V-bank so that the intake system is compactly disposed toward the cylinder banks.
An engine may comprise, according to the arrangement of cylinders, an in-line engine having cylinder banks arranged in series, or a V-type engine having cylinder banks arranged in a V-shape. The V-type engine includes first and second cylinder heads on generally a V-shaped cylinder block. First and second head covers are mounted on the cylinder heads to define first and second cylinder banks arranged in a V-shape.
A V-type engine 102 is shown in FIG. 7. The V-type engine 102 comprises first and second cylinder heads 106A, 106B on a generally V-shaped cylinder block 104, and first and second head covers 108A, 108B mounted on the cylinder heads 106A, 106B to define first and second cylinder banks 110A, 110B arranged in a V-shape. The cylinder banks 110A, 110B define a space 112 therebetween.
An intake system 114 of the V-type engine 102 comprises a first surge tank 116A above the cover 108B of the cylinder bank 110B, and a second surge tank 116B above the cover 108A of the cylinder bank 110A.
The surge tanks 116A, 116B are connected to one ends of respective first and second intake pipes 120A, 120B of an intake manifold 118. The intake pipes 120A, 120B extend from the respective surge tanks toward the opposite cylinder banks 110A, 110B, and have middle portions which intersect between the cylinder banks, and have the other ends thereof connected to the cylinder heads 106A, 106B of the cylinder banks 110A, 110B respectively.
The intake system 114 has a construction in which the first and second surge tanks 116A, 116B are disposed above the opposite second and first cylinder banks 110B, 110A, and the intake pipes 120A, 120B extend therefrom toward the opposite cylinder heads 106A, 106B. Accordingly, it is difficult to incorporate variable intake means which can change the intake pipe length.
An intake system of a V-type engine having variable intake means is disclosed in Japanese Patent No. 2541964, Japanese Patent Laid-Open No. 8-319813, and Japanese Patent Laid-Open No. 2000-186640.
The intake system disclosed in Japanese Patent No. 2541964 includes a volume above and between the banks, and first and second downstream intake passages connected to the banks and having downstream ends thereof intersecting below the volume. The intake passages are positioned in a cylinder-row direction in an alternating position. An intersection of the passages is positioned so as to be within the length of the volume in the cylinder-row direction. A first communication passage connects a lower part of the volume with the first intake passages. A second communication passage connects the lower part of the volume with the second intake passages. Valves are disposed in the communication passages and open the passages during high speed operation. The communication passages are arranged in two rows in the direction of the crankshaft axis.
The intake system disclosed in Japanese Patent Laid-Open No. 8-319813 comprises a plurality of branch pipes communicating to the opposing right and left banks formed in V-shape, a surge tank above the branch pipes to distribute intake air, a blowby gas passage to introduce blowby gas into the surge tank, an oil collect recess formed in a division wall dividing the surge tank and the branch pipes, and a hole for dropped oil connected to the oil collect recess and the branch pipes.
The intake system disclosed in Japanese Patent Laid-Open No. 2000-186640 has cylinders forming right and left banks arranged in V-shape or in horizontally opposed shape. Valves for opening and shutting main passages are positioned by one single shaft at the intersection of two main passages to the cylinders of the right and left banks. Sub passages have one ends opened toward the upstream side of the valve, and the other ends opened toward the downstream side thereof.
The intake system of the V-type engine disclosed in, e.g., Japanese Patent No. 2541964 includes a surge tank as a volume part above a space between first and second banks. An intersection or crossing of first and second downstream intake passages is positioned below the surge tank. First and second communication passages communicate a lower part of the surge tank with the intake passages. Valves are arranged in the passages to open and close the passage to vary the length of the intake passages.
However, in these intake systems, the crossing of the intake passages, the communication passages, and the valves are stacked in a vertical direction below the surge tank, causing the surge tank to protrude significantly above this space. As a result, the height dimension of the engine becomes large, which is disadvantageous when the engine is mounted to the vehicle.
In order to obviate or minimize the above problem or expense, the present invention provides an intake system of a V-type engine having a surge tank extending in a cylinder-row direction above a space between first and second cylinder banks of the V-type engine, a first intake pipe of a intake manifold having one end thereof connected to a second side of the surge tank which faces the second cylinder bank, and a second intake pipe of a intake manifold having one end thereof connected to a first side of the surge tank which faces the first cylinder bank, the first and second intake pipes having one ends thereof bent and turned in the vicinities of the second and first cylinder banks respectively, and having middle portions thereof intersected below the surge tank to have the other ends thereof connected to the first and second cylinder banks, the intake system comprising: the first and second intake pipes which are connected to the first and second cylinder banks respectively arranged in an alternating position in a cylinder-row direction; first and second branch pipes having one ends thereof connected into the surge tank and the other ends thereof connected to adjacent other ends of the first and second intake pipes; and variable intake means (e.g. valve elements) to open and close first and second branch passages of the branch pipes, the variable intake means being disposed at one ends of the first and second branch pipes which are inserted into the surge tank.
Such an intake system minimizes protrusion of the surge tank from the space between the cylinder banks since the variable intake means are disposed within the surge tank, whereas the variable intake means of a conventional intake system are disposed below the surge tank.
An intake system of a V-type engine is also disclosed in Japanese Patent Laid-Open No. 3-271558 and has primary and secondary ports opening toward a V-shaped space in the multi-cylinder V-type engine. The ports are connected to a surge tank within the V-shaped space through primary and secondary intake passages, respectively. A control-valve is provided in the secondary port to close and open at low and high engine speeds, respectively. The secondary intake passage extends upwardly from a cylinder in a slanting direction. The primary intake passage extends upwardly to detour the rotating shaft line of the control-valve. Thereby, a compact engine constitution is achieved.
Another intake system of an engine as disclosed in Japanese Patent Laid-Open No. 7-229424 has an intake air control valve for variable control of an intake passage area disposed within an intake passage connecting to a plurality of intake valve openings. The intake passage is divided into first and second passages. The second passage communicates with a part of the intake valve opening by a separate wall. The first passage communicates with the other intake valve opening. A second control valve controls the second passage to be fully closed when the quantity of intake air is small, and to be fully opened when the quantity of intake air is large. A first control valve controls the first passage to be closed such that only upward or outward portion thereof is opened when the quantity of intake air is small, and to be fully opened when the quantity of the intake air is large. This constitution, without an increased intake resistance, produces tumble or swirl flow reliably.
An intake system of a conventional V-type engine having a variable intake valve system, as shown in FIGS. 12 and 13, has been already provided commercially. Such a valve system comprises a surge tank, an intake manifold rolling around the surge tank in a counter clockwise direction, and a variable intake valve unit disposed between an upper part of the surge tank and the intake manifold. The variable intake valve of the variable intake valve unit is switched. That is, the variable intake valve is opened during high-speed operation as shown in FIG. 12, and is closed during low-speed operation as shown in FIG. 13. However, the flow out from the variable intake valve during high-speed operation is bent (i.e. curved) to a large degree, causing an increase in intake resistance and reducing output.
In order to obviate or at least minimize the above inconveniences, the present invention provides an intake system of a V-type engine having a surge tank disposed above and between first and second cylinder banks of the V-type engine, intake passages branching from sides of the surge tank and each intersecting below the surge tank to connect to each cylinder bank, the intake system comprising: first and second intake passages connected to the first and second cylinder banks respectively, and disposed below the surge tank in a cylinder-row direction; first and second branch passages branching from middle portions of the first and second intake passages respectively, and connected to a lower part of the surge tank, the first and second branch passage having center axes thereof inclined toward a center axis of the cylinder banks of the V-type engine, the two center axes intersecting within the surge tank; and a valve system to open and close the first and second branch passages, the valve system having a rotating shaft thereof penetrating at an intersection of the two center axes.
According to the present invention, the first and second branch passages for high speed operation are thus inclined toward the center axis between the cylinder banks which is a longitudinal center axis of the V-type engine. Accordingly, bending with the intake ports of the first and second cylinder heads having openings toward the center axis of the V-bank is prevented, so that the resistance of intake can be reduced. Also, an intersection of the first and second branch passages is positioned within the surge tank, so that the surge tank can be disposed at a lower position, which can reduce the height dimension of the intake system. Furthermore, the intersecting part can be penetrated by one single rotating shaft of the valve system for opening and closing of the first and second branch passages. Thereby, the surge tank having the valve system built-in can be miniaturized, which can reduce width dimension of the intake system.